Composition for high performance glass fibers and fibers formed therewith

ABSTRACT

A composition for the manufacture of high strength glass fibers suitable for manufacture in both precious metal lined furnaces and refractory lined glass melter is disclosed. The glass composition of the present invention includes 62-68 weight % SiO 2 , 22-26 weight % Al 2 O 3 , 8-15 weight % MgO and 0.1 to 3.0 weight % Li 2 O. One suitable composition of the present invention includes 64-66.5 weight percent SiO 2 , 23-24.5 weight percent Al 2 O 3 , 9-11 weight percent MgO and 0.3-0.35 weight percent Li 2 O. Another suitable composition includes 66.5 weight percent SiO 2 , 23.4 weight percent Al 2 O 3 , 9.8 weight percent MgO and 0.3 weight percent Li 2 O. Yet another suitable composition is about 66 weight percent SiO 2 , about 23 weight percent Al 2 O 3 , about 10.5 weight percent MgO and about 0.3 weight percent Li 2 O. Fibers formed by the present invention are also disclosed. The fibers have a fiberizing temperature of less than 2650° F., a ΔT of at least 25° F. Further, the glass fibers of the present invention typically have a strength in excess of 700 KPSI, in one embodiment, a strength in excess of about 730 KPSI, and, in yet another embodiment, a strength in excess of about 750 KPSI. The glass fibers will typically have a modulus greater than 12.8 MPSI, in one embodiment, greater than about 13 MPSI, and, in yet another embodiment, greater than about 13.2 MPSI.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention is generally directed to a composition for use inmanufacturing continuous high strength glass fibers and fibers formedfrom the composition.

BACKGROUND OF THE INVENTION

A common glass composition for making continuous high-strength glassfiber strands is “S-Glass.” The term S-Glass defines a family of glassescomposed primarily of the oxides of magnesium, aluminum, and siliconwith a chemical composition that produces glass fibers having a highermechanical strength than E-Glass fibers. The chemical composition of theS-glass family produces high strength glass fiber and enables theseglasses to be used in high strength applications such as ballisticarmor. ASTM International defines S-Glass as family of glasses composedprimarily of the oxides of magnesium, aluminum, and silicon with acertified chemical composition which conforms to an applicable materialspecification and which produces high mechanical strength (D578-05). TheDeutsches Institut für Normung (DIN) defines S-Glass as analuminosilicate glass without added CaO and having a partial mass of MgOwhere MgO is about 10% by weight (An alumino-silicate glass is definedas a glass which consists largely of aluminum trioxide and silicondioxide and other oxides) (DIN 1259-1).

U.S. Pat. No. 3,402,055, describes a composition for forming a highstrength glass within the S-Glass family. A commercially available highstrength S-Glass composition is S-2 Glass. As described in publicationWO/2004/094794, assigned on its face to 3M Innovative PropertiesCompany, S-2 glass fibers typically have a composition of about 65% OfSiO₂, 25% of Al₂O₃, and 10% of MgO. S-2 Glass is manufactured byAdvanced Glass Yarns, of Aiken S.C., USA. S-2 Glass has high compressiveand tensile strength and good high temperature properties. S-2 Glass isused in helicopter blades, armor and windings for high pressure tanks,such as scuba tanks.

R-Glass is another family of high strength, high modulus glasses that istypically formed into fibers for use in aerospace compositeapplications. The R-Glass family is primarily composed of silicon oxide,aluminum oxide, magnesium oxide, and calcium oxide with a chemicalcomposition that produces glass fibers with mechanical strength which isgenerally lower than S-Glass fibers. R-Glass generally contains lesssilica and greater calcium oxide (CaO) than S-Glass which requireshigher melting and processing temperatures during fiber forming. As alsodescribed in publication WO/2004/094794, R-glass fibers typically have acomposition of 60% of SiO₂, 25% of Al₂O₃, 9% of CaO and 6% of MgO.

Tables IA-IE set forth the compositions for a number of conventionalhigh strength glass compositions.

TABLE I-A NITTOBO Chinese RUSSIAN NITTOBO “T” Glass High CONTINUOUS “T”Fabric Strength ROVING MAGNESIUM Glass (Yarn) Constituent glassALUMINOSILICATE Fabric “B” “C” SiO₂ 55.08 55.81 64.58 64.64 CaO 0.330.38 0.44 0.40 Al₂O₃ 25.22 23.78 24.44 24.57 B₂O₃ 1.85 0.03 0.03 MgO15.96 15.08 9.95 9.92 Na₂O 0.12 0.063 0.08 0.09 Fluorine 0.03 0.0340.037 TiO₂ 0.023 2.33 0.019 0.018 Fe₂O₃ 1.1 0.388 0.187 0.180 K₂O 0.0390.56 0.007 0.010 ZrO₂ 0.007 0.15 Cr₂O₃ 0.011 0.003 0.003 Li₂O 1.63 CeO₂

TABLE I-B Nitto Nitto Vetrotex Saint Boseki Boseki Nitto Boseki TEGobain SR Glass Polotsk A&P NT6030 Glass RST- Stratifils SR CGSTEKLOVOLOKNO Constituent Yarn Yarn 220PA-535CS 250 P109 High StrengthGlass SiO₂ 65.51 64.60 64.20 63.90 58.64 CaO 0.44 0.58 0.63 0.26 0.61Al₂O₃ 24.06 24.60 25.10 24.40 25.41 B₂O₃ 0.04 MgO 9.73 9.90 9.90 10.0014.18 Na₂O 0.04 0.06 0.020 0.039 0.05 Fluorine 0.07 0.02 TiO₂ 0.0160.000 0.000 0.210 0.624 Fe₂O₃ 0.067 0.079 0.083 0.520 0.253 K₂O 0.0200.020 0.020 0.540 0.35 ZrO₂ 0.079 Cr₂O₃ 0.0010 0.001 0.023 Li₂O CeO₂

TABLE I-C Chinese Advanced High Glass Chinese High Strength YarnsStrength Yarn Glass Zentron S-2 SOLAIS Glass Constituent (8 micron)Roving Glass Roving Sample SiO₂ 55.22 55.49 64.74 64.81 CaO 0.73 0.290.14 0.55 Al₂O₃ 24.42 24.88 24.70 24.51 B₂O₃ 3.46 3.52 0.02 MgO 12.4612.28 10.24 9.35 Na₂O 0.104 0.06 0.17 0.16 Fluorine 0.07 0.02 TiO₂ 0.320.36 0.015 0.04 Fe₂O₃ 0.980 0.930 0.045 0.238 K₂O 0.240 0.150 0.005 0.03ZrO₂ Cr₂O₃ 0.0050 0.007 Li₂O 0.59 0.63 CeO₂ 1.23 1.25

TABLE I-D Advanced IVG Vertex Glass Yarns Culimeta IVG Vertex B96 IVGVertex Outside #1 Glass Constituent S Glass Roving 675 Yarn Glass RovingRoving SiO₂ 64.61 59.37 58.34 58.58 58.12 CaO 0.17 0.27 0.31 0.30 0.31Al₂O₃ 24.84 25.49 23.81 24.26 24.09 B₂O₃ 0.04 0.05 MgO 10.11 13.47 14.9915.02 15.36 Na₂O 0.118 0.024 0.05 0.02 0.03 Fluorine 0.03 0.04 0.04 0.04TiO₂ 0.011 0.530 1.380 0.67 0.91 Fe₂O₃ 0.042 0.374 0.333 0.336 0.303 K₂O0.48 0.42 0.28 0.29 ZrO₂ 0.152 0.129 0.165 0.157 Cr₂O₃ 0.0050 0.01200.0100 0.0120 0.0120 Li₂O CeO₂

TABLE I-E IVG Vertex RH CG250 P109 Outside #2 Glass Fiber ConstituentGlass Roving Strand SiO₂ 58.69 58.54 CaO 0.29 9.35 Al₂O₃ 24.3 25.39 B₂O₃MgO 15.06 6.15 Na₂O 0.03 0.10 Fluorine 0.04 0.16 TiO₂ 0.64 0.008 Fe₂O₃0.331 0.069 K₂O 0.36 0.14 ZrO₂ 0.187 0.006 Cr₂O₃ 0.0130 Li₂O CeO₂

SUMMARY OF THE INVENTION

The present invention is a glass composition for the formation ofcontinuous glass fibers suitable for use in high strength applications.Once formed into fibers, the glass composition provides the strengthcharacteristics of S-Glass. One composition of the present inventionincludes 62-68 weight percent SiO₂, 22-26 weight percent Al₂O₃, 8-15weight percent MgO and 0.1-2 weight percent Li₂O. In certainembodiments, the glass composition is composed of 64-66.5 weight percentSiO₂, 23-24.5 weight percent Al₂O₃, 9-11 weight percent MgO and 0.3-0.35weight percent Li₂O. In another embodiment, the glass composition iscomposed of 66.5 weight percent SiO₂, 23.4 weight percent Al₂O₃, 9.8weight percent MgO and 0.3 weight percent Li₂O. In another embodimentthe fiber is composed of about 66 weight percent SiO₂, about 23 weightpercent Al₂O₃, about 10.5 weight percent MgO and about 0.3 weightpercent Li₂O. In certain embodiments, the composition does not containmore than about 2.0 weight % of oxides or compounds selected from thegroup consisting of CaO, P₂O₅, ZnO, ZrO₂, SrO, BaO, SO₃, F₂, B₂O₃, TiO₂and Fe₂O₃. In certain embodiments the fiber has a modulus greater than12.8 MPsi and a pristine tensile strength of 700 KPsi. In anotherembodiment, the fiber has a modulus greater than about 13 MPsi and apristine tensile strength of about 750 KPsi.

The desired properties of the high performance composite fibersmanufactured by the present invention include a composition having afiberizing temperature of less than about 2650° F., or in one embodimentless than about 2625° F., in another embodiment less than about 2600° F.and in yet another embodiment less than about 2575° F. and a liquidustemperature that is, in one embodiment, below the fiberizing temperatureby at least 25° F., in another embodiment, by at least about 50° F.,and, in yet another embodiment, by at least about 75° F.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

The fiberizing properties of the glass batch composition of the presentinvention include the fiberizing temperature, the liquidus, and delta-T(ΔT). The fiberizing temperature is defined as the temperature thatcorresponds to a viscosity of 1000 Poise. As discussed in more detailbelow, a lowered fiberizing temperature reduces the production cost ofthe fibers, allows for a longer bushing life, increases throughput andreduces energy consumption. For example, at a lower fiberizingtemperature, a bushing operates at a cooler temperature and does not“sag” as quickly. Sag is a phenomenon that occurs in bushings that areheld at an elevated temperature for extended periods of time. Bylowering the fiberizing temperature, the sag rate of the bushing may bereduced and the bushing life can be increased. In addition, a lowerfiberizing temperature allows for a higher throughput since more glasscan be melted in a given period at a given energy input. As a result,production cost is reduced.

The liquidus of a glass is defined as the highest temperature at whichequilibrium exists between liquid glass and its primary crystallinephase. At all temperatures above the liquidus, the glass is free fromcrystals in its primary phase. At temperatures below the liquidus,crystals may form. Crystals in the melt will cause blockages in thebushing and weakness in the fibers.

Another fiberizing property is delta-T (ΔT), which is defined as thedifference between the fiberizing temperature and the liquidus. A largerΔT offers a greater degree of flexibility during the formation of theglass fibers and helps to inhibit devitrification of the glass (that is,the formation of crystals within the melt) during melting andfiberizing. Increasing the ΔT also reduces the production cost of theglass fibers by allowing for a greater bushing life and by providing awider process window for forming fibers.

The glasses of the present invention are typically continuously meltedin precious metal lined containers using a platinum electric heater. Theglasses may be suitable for melting in traditional commerciallyavailable refractory-lined glass melters that are widely used in themanufacture of glass reinforcement fibers. Starting batch componentstypically include SiO₂ (ground silica sand), and Al₂O₃ (calcinedalumina) or pyrophyllite, as well as chain modifiers from sourcematerials such as talc, magnesite or dolomite. The carbon included inmaterials such as magnesite is off gassed as oxides of carbon such asCO₂.

A fiber formed in accordance with the present invention will typicallyinclude 62-68 weight percent SiO₂, 22-26 weight percent Al₂O₃, 8-15weight percent MgO and 0.1-2 weight percent Li₂O. In certainembodiments, the glass composition is composed of 64-66.5 weight percentSiO₂, 23-24.5 weight percent Al₂O₃, 9-11 weight percent MgO and 0.3-0.35weight percent Li₂O. In another embodiment, the glass composition iscomposed of 66.5 weight percent SiO₂, 23.4 weight percent Al₂O₃, 9.8weight percent MgO and 0.3 weight percent Li₂O. In another embodimentthe fiber is composed of about 66 weight percent SiO₂, about 23 weightpercent Al₂O₃, about 10.5 weight percent MgO and about 0.3 weightpercent Li₂O. In certain embodiments, the composition does not containmore than about 2.0 weight % of oxides or compounds selected from thegroup consisting of CaO, P₂O₅, ZnO, ZrO₂, SrO, BaO, SO₃, F₂, B₂O₃, TiO₂and Fe₂O₃. A fiber formed in accordance with the present invention willtypically include small amounts of CaO, P₂O₅, ZnO, ZrO₂, SrO, Ba, SO₃,F₂, B₂O₃, TiO₂ and Fe₂O₃, typically in a total amount of less than 3weight percent, and in another embodiment less than about 2 weightpercent. In addition, a fiber formed in accordance with the method andcomposition of the present invention will typically have a fiberizingtemperature of less than 2650° F., in another embodiment less than about2625° F., in yet another embodiment less than about 2600° F. and, in yetanother embodiment, less than about 2575° F. and a liquidus temperaturethat is typically below the fiberizing temperature by at least 25° F.,in one embodiment, by at least about 50° F., and, in yet anotherembodiment, by at least about 75° F. Further, the glass of the presentinvention typically will have a pristine fiber tensile strength inexcess of 700 KPSI, in one embodiment, a strength in excess of about 730KPSI, and, in yet another embodiment, a strength in excess of about 750KPSI. Further, the glass fibers will typically have a modulus greaterthan 12.8 MPSI, in one embodiment, greater than about 13.0 MPSI, and inyet another embodiment, greater than about 13.2 MPSI.

The melted glass is delivered to a bushing assembly from a platinumlined melting chamber which is heated electrically. The bushing includesa tip plate with a plurality of nozzles; each nozzle discharges a streamof molten glass, which is mechanically drawn to form continuousfilaments. Typically, the filaments are coated with a protective sizing,gathered into a single continuous strand and wound onto a rotatingcollet of a winder device to form a package. The filaments may also beprocessed into other forms including, without limitation, wet usedchopped strand fibers, dry use chopped strand fibers, continuousfilament mats, chopped strand mats, wet formed mats or air laid mats.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples illustrated belowwhich are provided for purposes of illustration only and are notintended to be all inclusive or limiting unless otherwise specified.

EXAMPLES

The glasses in the examples listed in Tables IIA-IID were melted inplatinum crucibles or in a continuous platintim-lined melter fordetermining the mechanical and physical properties of the glass andfibers produced there from. The units of measurement for the physicalproperties are: Viscosity (° F.), Liquidus temperature (° F.) and ΔT (°F.). In some examples the glasses were fiberized and Strength (KPsi),Density (g/cc), Modulus (MPsi) were measured.

The fiberizing temperature was measured using a rotating spindleviscometer. The fiberizing viscosity is defined as 1000 Poise. Theliquidus was measured by placing a platinum container filled with glassin a thermal gradient furnace for 16 hours. The greatest temperature atwhich crystals were present was considered the liquidus temperature. Themodulus was measured using the sonic technique on a single fiber ofglass. The tensile strength was measured on a pristine single fiber.

TABLE IIA Glass Ex. 1 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 SiO₂ 62 62 66.0563.05 66.05 66.05 Al₂O₃ 22 22 24.05 23.55 23.05 23.05 MgO 14 15 9.5513.05 9.55 10.55 Li₂O 2 1 0.35 0.35 1.35 0.35 Measured 2389 2433 26262499 2506 2603 Viscosity (° F.) 1^(st) Measured 2410 2466 2609 2551 25712577 Liquidus (° F.) 2^(nd) Measured 2426 2491 2623 2545 2545 2574Liquidus (° F.) ΔT (° F.) −29 −45.5 10 −49 −52 27.5 Measured 2.53332.5418 2.4773 2.5251 2.4745 2.4845 Density (g/cc)

TABLE II-B Glass Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 SiO₂ 63.05 6263.55 64.1 64 63.05 Al₂O₃ 23.05 28 23.05 24.1 26 23.05 MgO 13.05 8 13.0511.1 9.55 12.55 Li₂O 0.85 2 0.35 0.7 0.35 1.35 Measured 2486 2513 25102549 2619 2479 Viscosity (° F.) 1^(st) Measured 2539 2646 2581 2594 26962502 Liquidus (° F.) 2^(nd) Measured 2566 2636 2566 2564 2664 2535Liquidus (° F.) ΔT (° F.) −66.5 −128 −63.5 −30 −61 −39.5 Measured 2.52392.4910 2.5205 2.5013 2.5004 2.5160 Density (g/cc)

TABLE II-C Glass Ex. 14 Ex. 15 Ex. 16 Ex. 17 SiO₂ 63.05 66.5 66.5 63.05Al₂O₃ 26.05 23.4 23.4 26.05 MgO 10.55 9.8 9.8 9.55 Li₂O 0.35 0.3 0.31.35 Measured 2564 2651 2659 2550 Viscosity (° F.) 1^(st) Measured 26162587 2540 2521 Liquidus (° F.) 2^(nd) Measured 2627 2600 2562 2550Liquidus (° F.) ΔT (° F.) −57.5 57.5 108 14.5 Measured 2.5130 2.4975Density (g/cc)

In Table II-C (above) Ex. 15 is the same composition as Ex. 16, howeverEx. 15 has been formed with reagent grade raw materials.

The fibers of Example 7 have a Measured Modulus of 13.04 MPsi and aMeasured Strength of 739 KPsi. The fibers of Example 12 have a MeasuredModulus of 13.21 MPsi and a Measured Strength of 751 KPsi. The fibers ofthe present invention have superior modulus and strengthcharacteristics. The fibers of Example 15 have a Measured Modulus of13.04 MPsi and a Measured Strength of 753 KPsi

As is understood in the art, the above exemplary inventive compositionsdo not always total 100% of the listed components due to statisticalconventions (such as, rounding and averaging) and the fact that somecompositions may include impurities that are not listed. Of course, theactual amounts of all components, including any impurities, in acomposition always total 100%. Furthermore, it should be understood thatwhere small quantities of components are specified in the compositions,for example, quantities on the order of about 0.05 weight percent orless, those components may be present in the form of trace impuritiespresent in the raw materials, rather than intentionally added.

Additionally, components may be added to the batch composition, forexample, to facilitate processing, that are later eliminated, therebyforming a glass composition that is essentially free of such components.Thus, for instance, minute quantities of components such as fluorine andsulfate may be present as trace impurities in the raw materialsproviding the silica, calcia, alumina, and magnesia components incommercial practice of the invention or they may be processing aids thatare essentially removed during manufacture.

As apparent from the above examples, glass fiber compositions of theinvention have advantageous properties, such as low fiberizingtemperatures and wide differences between the liquidus temperatures andthe fiberizing temperatures (high ΔT values). Other advantages andobvious modifications of the invention will be apparent to the artisanfrom the above description and further through practice of theinvention). The high-performance glass of the present invention meltsand refines at relatively low temperatures, has a workable viscosityover a wide range of relatively low temperatures, and a low liquidustemperature range.

The invention of this application has been described above bothgenerically and with regard to specific embodiments. Although theinvention has been set forth in what is believed to be the preferredembodiments, a wide variety of alternatives known to those of skill inthe art can be selected within the generic disclosure. Other advantagesand obvious modifications of the invention will be apparent to theartisan from the above description and further through practice of theinvention. The invention is not otherwise limited, except for therecitation of the claims set forth below.

1. A high strength glass fiber comprising: 62-68 weight percent SiO₂;22-26 weight percent Al₂O₃; 8-11.1 weight percent MgO; 0.1-3.0 weightpercent Li₂O; and less than 2 weight percent CaO, wherein said fiber hasa pristine fiber tensile strength greater than 700 KPSI and a fiberizingtemperature less than about 2650° F.
 2. The high strength glass fiber ofclaim 1, further comprising: less than about 3 weight percent total ofone or more compounds selected from the group consisting of P₂O₅, ZnO,ZrO₂, SrO, BaO, S0₃ F₂, B₂O₃, TiO₂ and Fe₂O₃.
 3. The high strength glassfiber of claim 1, wherein said SiO₂ is present in said glass in amountbetween 64 and 67 weight percent.
 4. The high strength glass fiber ofclaim 1, wherein said fiber has a modulus greater than about 12.8 MPSI.5. The high strength glass fiber of claim 1, wherein said fiber has aliquidus temperature that is at least 25° F. less than said fiberizingtemperature.
 6. The high strength glass fiber of claim 1, wherein: saidSiO₂ is present in said fiber in an amount from about 64 to about 66.5weight percent; said Al₂O₃ is present in said fiber in an amount fromabout 23 to about 24.5 weight percent; said MgO is present in said fiberin an amount from about 9 to about 11 weight percent; and said Li₂O ispresent in said fiber in an amount from about 0.1 to about 2.0 weightpercent.
 7. The high strength glass fiber of claim 1, wherein said fiberhas a delta T of at least 25° F.
 8. The high strength glass fiber ofclaim 1, wherein said Li₂O is present in said fiber in an amount from1.75 to 3.0 weight percent.
 9. A composition for forming a glass fibercomprising: SiO₂ in an amount from about 62 to about 68 weight percent;Al₂O₃ in an amount from about 22 to about 26 weight percent; MgO in anamount from about 8 to about 11.1 weight percent; Li₂O in an amount fromabout 0.1 to about 3 weight percent; and less than 2 weight percent CaO,wherein said fiber has a pristine fiber tensile strength greater than700 KPSI.
 10. The composition of claim 9, further comprising less thanabout 3 weight percent total of one or more compounds selected from thegroup consisting of P₂O₅, ZnO, ZrO₂, SrO, BaO, SO₃, F₂, B₂O₃, TiO₂ andFe₂O₃.
 11. The composition of claim 9, wherein: said SiO₂ is present insaid fiber in an amount from about 64 to about 66.5 weight percent; saidAl₂O₃ is present in said fiber in an amount from about 23 to about 24.5weight percent; said MgO is present in said fiber in an amount fromabout 9 to about 11 weight percent; and said Li₂O is present in saidfiber in an amount from about 0.1 to about 2.0 weight percent.
 12. Thecomposition of claim 9, wherein said Li₂O is present in said fiber in anamount from 1.75 to 3.0 weight percent.